In a small bowl, mix together vinegar, water, soy sauce, sugar, and garlic.
Set pressure cooker (Insta Pot) to sauté, add oil and let heat 1-2 minutes.
Season pork with salt and pepper, place in pressure cooker, brown on all sides, 2-3 minutes per side.
Add sauce and set the pressure cooker to meat setting and set the timer for 15 minutes per pound (3lb roast = 45 minutes).
Allow pressure to release on it's own. Remove from pressure cooker and let it rest covered for 20 minutes before slicing.
While the pork is resting, set pressure cooker to sauté. In a small bowl whisk together the cornstarch and water, add to the pressure cooker, whisk until thickened. Serve over pork